Carbohydrate ingestion attenuates the increase in plasma interleukin-6, but not skeletal muscle interleukin-6 mRNA, during exercise in humans

Abstract

1. The present study was undertaken to examine the effects of exercise and carbohydrate (CHO) ingestion on interleukin-6 (IL-6) gene expression in skeletal muscle and plasma IL-6 concentration. 2. Seven moderately trained men completed 60 min of exercise at a workload corresponding to each individual's lactate threshold on four randomised occasions. Two trials were conducted on a bicycle ergometer (Cyc) and two on a running treadmill (Run) either with (CHO) or without (Con) the ingestion of a CHO beverage throughout the exercise. Muscle biopsies were obtained from the vastus lateralis before and immediately after exercise and IL-6 gene expression in these samples was determined using real-time PCR. In addition, venous blood samples were collected at rest, and after 30 min during and at the cessation of exercise. These samples were analysed for plasma IL-6. 3. Irrespective of exercise mode or CHO ingestion, exercise resulted in a 21 +/- 4-fold increase (P < 0.01; main exercise effect) in IL-6 mRNA expression. In contrast, while the mode of exercise did not affect the exercise-induced increase in plasma IL-6, CHO ingestion blunted (P < 0.01) this response. 4. These data demonstrate that CHO ingestion attenuates the plasma IL-6 concentration during both cycling and running exercise. However, because IL-6 mRNA expression was unaffected by CHO ingestion, it is likely that the ingestion of CHO during exercise attenuates IL-6 production by tissues other than skeletal muscle.

Figure 1. Plasma glucose concentrations during 60 min of cycling (Cyc) or running (Run) exercise either with (CHO) or without (Con) the ingestion of a CHO solution during exercise

Values are means ± s.e.m. (n = 7). *P < 0.05, **P < 0.01, † P < 0.001, Con significantly different from CHO trial.

Figure 2. Muscle glycogen content prior to (Pre) and following (Post) 60 min of cycling (Cyc) or running (Run) exercise either with (CHO) or without (Con) the ingestion of a CHO solution during exercise

Values are means ± s.e.m. (n = 7). **P < 0.01, main time effect Post different from Pre.

Figure 3. Change in IL-6 mRNA expression in human skeletal muscle from pre-exercise to post-exercise following 60 min of cycling (Cyc) or running (Run) exercise either with (CHO) or without (Con) the ingestion of a CHO solution during exercise

Values are means ± s.e.m. (n = 7). **P < 0.01, main time effect.

Figure 4. Plasma IL-6 concentration prior to (Rest), after 30 min and immediately following 60 min of cycling (Cyc) or running (Run) exercise with (CHO) or without (Con) the ingestion of a CHO solution throughout exercise

Values are means ± s.e.m. (n = 7). **P < 0.01, main time effect post-exercise different from pre-exercise. *P < 0.01, time × drink interaction.